Conventionally, incandescent light bulbs have been used for many lighting purposes. The incandescent light bulb, also referred to as an incandescent lamp or incandescent globe, is a source of light resulting from incandescence. Incandescence refers to heat-driven light emissions. In the incandescent light bulb, a thin filament is enclosed in a glass bulb that holds a vacuum or an inert gas. An electric current is supplied to the filament heating the filament to a temperature that produces light. The incandescent bulb typically produces a broad spectrum light that is inherently non-directional. The incandescent bulb also emits a large amount of heat relative to emitted light. For energy conservation purposes and for heat management purposes, alternatives to incandescent bulbs are sought.
A light-emitting diode (LED) is a semiconductor light source that operates through electroluminescence. Forward biased electric current through an LED causes the LED to emit photons. An LED is a highly efficient light source particularly in comparison to incandescent lamps. An LED typically radiates much less heat than an incandescent lamp. LEDs, however, produce light that is directional and so LEDs are generally undesirable for use in applications where a spherical light field is sought.